Brightness differences influence the evaluation of affective pictures

Abstract

We explored the possibility of a general brightness bias: brighter pictures are evaluated more positively, while darker pictures are evaluated more negatively. In Study 1 we found that positive pictures are brighter than negative pictures in two affective picture databases (the IAPS and the GAPED). Study 2 revealed that because researchers select affective pictures on the extremity of their affective rating without controlling for brightness differences, pictures used in positive conditions of experiments were on average brighter than those used in negative conditions. Going beyond correlational support for our hypothesis, Studies 3 and 4 showed that brighter versions of neutral pictures were evaluated more positively than darker versions of the same picture. Study 5 revealed that people categorised positive words more quickly than negative words after a bright picture prime, and vice versa for negative pictures. Together, these studies provide strong support for the hypotheses that picture brightness influences evaluations.

Keywords:

• Affective pictures
• Emotions
• Brightness bias
• IAPS
• Colour psychology

We thank Dik Hermes for valuable assistance with MATLAB programming.

We thank Dik Hermes for valuable assistance with MATLAB programming.

Notes

¹ Note that several IAPS pictures have two sets of ratings in the 2008 Tech manual for pictures that were included in two separate rating studies: 1230, 1590, 1610, 1640, 1670, 2210, 3000, 3010, 4220, 4520, 6200, 9090. The first reported set of ratings was used in the current analysis, but both ratings yielded identical results.

² One study used only nine exceptionally bright positive pictures, one study used only two exceptionally bright neutral pictures, and one study used only two exceptionally bright negative pictures.

³ Note that the interaction was also significant without removing outliers, F(1, 77)=5.39, p=.023, , or when using an a priori determined cutoff value of 1,000 ms (cf. Gawronski, Deutsch, & Seidel, 2005), F(1, 77)=25.76, p<.001, .